Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/114

82 of distinct germinal masses, which unite whilst free in the welter, to form a spore, a process corresponding to the so-called conjugation of the Spirogyra.

The red or rose-colored Algae, though much smaller than the Fucoidae, surpass them greatly in beauty of coloring and delicacy of form. They are commonly known as red sea-weed, and, when dried and arranged on paper, they are often offered for sale. The Floridae (Fig. 101), or Red Algae, are from six inches to two feet high, offering in their coloring different shades of red, rose-red, and purple. Their form varies from that of a filament or stalk to that of a leaf or feather. To see them in perfection, they must be studied in a tropical climate. The reproduction of the Floridae is still involved in some mystery. There are in many species tetraspores (Fig. 102), which are formed by the division of the so-called perispore into four spores, which appear to correspond with the zoospores of the lower Algae. Besides these tetraspores, other reproductive bodies arise in some species from the union of two germs, which may be looked upon as the representatives of distinct sexes. While the Green, Brown, and Red Algae differ greatly in their size, form, coloring, and reproduction, they all agree in their cellular structure. When we compare a single individual of the Chlorococcus—so minute that hundreds of thousands might rest on the head of a knitting-needle—with the gigantic Macrocystis, notwithstanding minor differences, we find the essentially cellular structure of both to be the same. The group of Algae is, therefore, a natural one, the extremes being connected by innumerable links, offering a gradual transition from microscopic forms to the largest of plants. In the preceding chapter we have given reasons for supposing it probable